Long before Twitter, the key social network in New York City was the soapbox.

“People would get up on boxes in Union Square and in front of the old Jewish Forward newspaper building to talk about labor and other issues,” says Annie Polland. “They’d talk about government and how to improve their lives.”

The working-class stiffs who listened to them often lived in apartments like the ones recreated at the Lower East Side Tenement Museum, whose exhibits are overseen by Polland — the author, with Daniel Soyer, of “Emerging Metropolis: New York Jews in the Age of Immigration,” winner of the 2012 Jewish Book Award.

Here, in honor of Labor Day, are four books she believes speaks best to the working-class experience in America.

Out to Work by Alice Kessler-Harris

There’s been so much debate about women and work lately, and while many turn to Sheryl Sandberg’s “Lean In” for advice, I find more inspiration in this fascinating history charting 300 years of women’s work — when and how they earned wages and how that impacted ideas about family responsibilities.

Jewish Radicals by Tony Michels

In this documentary collection, we hear the voices of workers, leaders, writers and orators. Some speeches remain incredibly relevant: Rose Pastor Stokes on the right to birth control, Pauline Newman on the importance of great teachers. Some recall a bygone New York, when Union Square was where people “gathered to make revolution and stayed to talk.”

Out of the Shadow by Rose Cohen

In this autobiography, 12-year-old Rahel leaves Russia for New York’s Lower East Side in the 1890s, where she lives in a tenement apartment with her father and toils in a sweatshop to earn enough money to bring over her mother and younger siblings. Though the work is tedious, her fierce hope for a better life keep the reader riveted.

Inheriting the City by Philip Kasinitz and others

The spirit of turn-of-the-20th-century Rose Cohen finds itself in the form of turn-of-the-21st-century Dominican, Chinese, West Indian, South American and Soviet Jewish immigrant teenagers. This masterful study assesses how culture, race and community shape New York’s new immigrants and how, in turn, their work and ideas shape New York’s future.